1. Field of the invention
The present invention relates to a variable magnification viewfinder device capable of changing viewfinder magnification and a method for changing luminance of information displayed in a viewfinder.
2. Description Related to the Prior Art
Digital cameras which convert an optical image into an electric signal by the use of an image sensor such as a CCD image sensor and store the electric signal as image data in a memory card or the like are widely used. Most of the digital cameras are provided with an LCD panel on the back. The LCD panel allows checking a subject image (through image) to be taken and reproduction and display of an image which has been recorded in the memory card.
Image capture with the digital camera is often performed outdoors under daylight. It may be hard to see an image on the LCD panel depending on a direction of outdoor light. A digital camera provided with a window-type viewfinder device in addition to the LCD panel is commercially available. There are optical window-type viewfinders, with which a subject is directly observed through a viewfinder optical system, and electronic window-type viewfinders, in which an electronic display panel such as a liquid crystal panel or an organic EL is disposed to display an image (through image) of a subject.
Taking lenses include fixed lenses and interchangeable lenses. The fixed lens is fixed to a camera body. The interchangeable lens is attached to the camera body in a removable manner. Furthermore, the taking lenses include fixed-focus lenses and variable power lenses including zoom lenses. The focal length of the fixed-focus lens is invariable. The focal length of the variable power lens is changeable. The camera using the interchangeable lens and/or the variable power lens captures images at various focal lengths. Hence, it is preferable that the viewfinder device is also adaptable to the focal lengths. Optical viewfinder devices each with visual field frames corresponding to different focal lengths and variable magnification viewfinder devices capable of adjusting viewfinder magnification are known. Optical viewfinder devices which display imaging conditions, for example, information of an f-number that represents brightness of the taking lens, the focal length of the taking lens, the shutter speed, and the imaging distance in the viewfinder field of view are also known. For example, Japanese Patent Laid-Open Publication No. 8-43918 discloses an optical viewfinder device which displays information such as a focus state of a taking lens on an LCD to allow viewing the displayed information through a viewfinder.
The optical viewfinder device disclosed in the Japanese Patent Laid-Open Publication No. 8-43918 changes brightness of the viewfinder field of view as the viewfinder magnification changes. Thereby the inside of the viewfinder is lighted or darkened. However, brightness of the displayed information such as characters on the LCD does not change, so that it may become difficult to read the information or the information may even become illegible. The brightness of the viewfinder field of view suddenly changes particularly in the variable magnification viewfinder device in which the viewfinder magnification is changed by inserting or retracting the variable power lens into or from the viewfinder optical path. The sudden change in the brightness makes illegibility of the displayed information noticeable.